A touchpad or trackpad is a device, normally on laptops, which does the same thing as a mouse by tracking the movement of the user's fingers.
The touchpad is a touch device, used in portable computers, to replace the mouse, using touch-sensitive cells. Currently, the touchpad identify vectors x and y using the capacitance provided by the skin of the fingers (or an object conducting electricity) on its surface, then the microprocessor determines the value of the load and knows which cells were pressed. To generate a movement, which he identifies the first and which last pressed cells, generating straight lines at intervals of milliseconds. These lines generated every millisecond together form the cursor movement.
The previous models used pressure sensors, but this system is no longer used in current touchpads - such as laptops, in particular - for not having the same quality and durability of new technologies.